California's data challenges EPA

"I'll be interested to see how [Department of Justice lawyers acting for the EPA] parse their way through this one. It won't be easy," says Bruce Buckheit, an environmental consultant who directed the EPA's air-enforcement division until 2003.

The EPA declined to comment on the lawsuits Wednesday, though it reiterated comments Mr. Johnson made last month when he said the Bush administration was "moving forward with a clear national solution – not a confusing patchwork of state rules" to cut vehicle emissions. The EPA also said the new national fuel-economy standard "would be more effective than a partial state-by-state approach."

But according to California's newly unveiled analysis, the US Corporate Average Fuel Economy (CAFE) statute, which mandates a 35-mile-per-gallon fleet average by 2020, would cut greenhouse gas emissions by only 8 million metric tons – compared with 17 million metric tons by 2016 for California's plan.

If a dozen other states that have already adopted California's proposed standards joined the Golden State, the impact would reduce greenhouse tailpipe emissions by nearly 60 million metric tons nationwide by 2020 – about 60 percent more than would be accomplished by CAFE, the California analysis showed.

EPA has yet to unveil its own technical analysis, which is expected to support Johnson's contention that the CAFE law is a superior mechanism. Also yet to be unveiled is EPA's legal argument.

Hints as to EPA's legal position may be found, however, in Johnson's Dec. 19 letter to Gov. Arnold Schwarzenegger denying California's request. It was, he said, fundamentally different from past waivers the EPA has granted. But legal analysts say EPA's basis for denying California must go further and pass four legal tests under the Clean Air Act, including: